Good animal models of psychopathology greatly facilitate research on both the behavioral/experiential aspects of such disorders, and their biological bases. It is rapidly becoming accepted that evolved neurobehavioral defense systems are involved in a range of emotion-linked behavior disorders such as anxiety and depression. The objective of this proposal is to characterize the defense systems of laboratory rats and mice and their wild cogenors, providing an empirical and conceptual basis for understanding the relationships of these behaviors to crucial features of eliciting threat stimuli and situations, as well as the mechanisms which control the progression from one defensive behavior to another under normal and abnormal circumstances. These studies will focus on recently described aspects of defense, including risk assessment, movement changes associated with defense, and potentially communicatory defensive ultrasounds. These and other defensive behaviors will be systematically evaluated in two groups previously shown to demonstrate enhanced defensiveness, females, and subordinate males living under chronic social stress; these are counterparts also to two human groups at greater risk for emotional disorders. Microanalyses of particular behaviors will attempt to differentiate specific patterns of defense changes associated with chronic and acute stressors. Finally, the project will attempt to develop models for precise, rapid, testing of a full range of defensive behaviors in mice, the animals of choice for research on the pharmacology of anxiety and depression. These mouse models, along with those developed previously in this project for the rat, should enable an exponential improvement in precision of measurement of defensive behaviors, and in the relevance of the behaviors measured for an understanding of human emotional pathology.